The K-T Asteroid: Would Modern Instrumentation Have Seen It Coming?

[Sunspace]

@Darren_Garrison

…So let’s pick round number times–10 hours, 10 minutes, 10 seconds (and ignore complicating issues such as the angle it arrived from.) At 10 hours, it would be 720,000 km away and cover around 0.047 minutes of arc, or roughly 1/10th the diameter of Mars viewed from Earth. At 10 minutes, it would be 12,000 km away and cover 2.86 minutes of arc, or roughly 1/10th the diameter of the moon viewed from Earth. At 10 seconds, it would be 200 km away and cover 172 minutes of arc, or close to 6 times the diameter of the moon viewed from…

Has anyone done a video of this?

[Darren_Garrison]

@Sunspace

Has anyone done a video of this?

A real-time video of what it would look like as it slowly grew in size from the POV of Earth’s surface over a number of hours? Probably not–it’d be pretty dull up until the end.

[Chronos]

On the other hand, if you blast the object into a large enough cloud of shotgun pellets, then some fraction of the cloud will miss the Earth, and that would be a real benefit.

[markn_1]

@Darren_Garrison

A real-time video of what it would look like as it slowly grew in size from the POV of Earth’s surface over a number of hours? Probably not–it’d be pretty dull up until the end.

Videos of asteroids hitting the Earth are almost always unrealistically speeded up. In reality, if you were at a viewpoint where the Earth looked to be the size of a basketball (1 inch = 1000 miles), an asteroid traveling at a typical speed of 40,000 miles per hour would look like it was moving a little over a half inch per minute. You’d be hard pressed to even tell that it was moving.

[jharvey963]

@Alessan

I get that anyone within a few thousand miles of the point of impact would be toast either way. That goes without saying. It’s just that I was under the impression that another aspect of a dinosaur-killer’s impact would be the nuclear winter caused by the billions of tons of water and/or dirt blown into the atmosphere by its impact. If most of it is burned up in the atmosphere, would that still happen? Or is that basically irrelevant?

Stranger on a Train is definitely the expert on this issue, but I’ll take a chance and hope that I don’t embarrass myself too badly. The “old” idea is that the asteroid would cause a nuclear winter scenario: sun light is blocked out, plants die, herbivores die, predators die. However, and this may still be controversial and not universally accepted, a new theory is that the mass extinction happened world wide within HOURS of impact, not months or years. How? The amount of matter vaporized and ejected into space was unimaginably huge. Scientists estimate that the impact crater was 20 miles deep and 100 miles wide. Take a minute to picture that. TWENTY MILES DEEP! Much or most of this material was ejected into space above the atmosphere, condensed once it reached the cold of space, circled the earth, and reentered the atmosphere (world wide), burning up as it did so.

This next is paraphrased from the PBS Documentary, The Day the Dinosaurs Died:
<Cue dramatic music>
As this material returned to earth…

The sky turned red…
Lava fell from the sky…

And the Entire

                 World

                          Burned...

The world-wide firestorm incinerated any land animal without underground or underwater shelter.

So under this hypothesis, the title of the Documentary – the DAY the Dinosaurs Died – is literally true.

Can’t type any more now. Past my bedtime.

J.

[Measure_for_Measure]

I understand that large aquatic creatures perished during the K-T event as well. So presumably a precipitous drop in sunlight and consequent collapse of the ocean’s ecosystem played a role as well.

[Chronos]

Or there’s sufficient interaction between the land and water ecosystems that the loss of so many land species affected the ocean, too.

[Earl_Snake-Hips_Tucker]

I saw a doc on the KT event and (if I’m remembering correctly), and one of the interviewees said that the submarine impact site might have taken. . . . 300,000 years to finally cool off!

[Darren_Garrison]

@Earl_Snake-Hips_Tucker

I saw a doc on the KT event and (if I’m remembering correctly), and one of the interviewees said that the submarine impact site might have taken. . . . 300,000 years to finally cool off!

That sounds like too many zeros.

[HeyHomie]

@DesertDog

Here is the horrifically fascinating Last Day of the Dinosaurs. I start it about 11 minutes in, twenty minutes before impact.

Fascinating indeed!

Do we know that it came from the south like that, or is that artistic license on the part of the video-makers?

[Irishman]

Yeah, looking at the impact crater and the subsequent shaping has determined the direction and angle of impact.

This article was linked to the first one: Russian scientists use lasers to destroy mini asteroids

Scientists used laser pulses to mimic the shockwaves produced by a nuclear bomb explosion. While blasting the model space rocks with the laser, researchers measured the distribution and movement of heat and pressure across the tiny asteroids.

Their experiments produced results similar to those predicted by computer simulations. But researchers found the total destruction of the model asteroids required nearly twice as much force per unit of mass as the force needed to disintegrate the Chelyabinsk meteor.

The experiments also proved a succession of small explosive forces was no more efficient than a single large explosion for the destruction of the mini asteroids.

The data suggests an Earth-threatening nonmetallic asteroid measuring 600 feet across would require a 3-megaton bomb.

In followup tests, scientists plan on measuring the effects of explosive forces on asteroids with different shapes and compositions.

They made model asteroids based on the Chelyabinsk asteroid, then baked them with lasers to measure the effects. This was used to validate computer simulations.

From the first article by Darren Garrison:

“Successful disruption requires ensuring that the asteroid pieces are sufficiently small and well-dispersed, so that they pose a much-reduced threat to the Earth,” Syal said. “Disruption carried out as late as tens of days before impact can still be very effective in reducing the total damage felt by Earth. Previous work by our research group has shown that the impacting debris is reduced to less than 1 percent of its initial mass by disrupting the asteroid, even at these late times.”

That seems at odds with the consensus here.

[Grey]

To be fair, we’re discussing a body 10,000 m in diameter while this team is reviewing one 200 m across. Assuming spherical cows there’s a volume difference of about 125,000.

[A_Dodgy_Dude]

@SamuelA

As for if humans were watching for it- during the night an object like that would be visible if you were looking in the right place. It would grow increasingly brighter over time.

I don’t understand why it gets brighter over time. A dark object … six miles across … moving at 45,000 mph. No atmosphere to create friction. How bright could sunshine make it? Wouldn’t we see it only for a few minutes before it struck?

[Saint_Cad]

@A_Dodgy_Dude

I don’t understand why it gets brighter over time. A dark object … six miles across … moving at 45,000 mph. No atmosphere to create friction. How bright could sunshine make it? Wouldn’t we see it only for a few minutes before it struck?

Inverse square law. Halve its distance to Earth and it’s 4 times brighter.

[Stranger_On_A_Train]

@A_Dodgy_Dude

I don’t understand why it gets brighter over time. A dark object … six miles across … moving at 45,000 mph. No atmosphere to create friction. How bright could sunshine make it? Wouldn’t we see it only for a few minutes before it struck?

How bright it would be to the eye depends on the albedo, but any object approaching the Sun will get brighter in infrared over time and distinguishable from the 2.7 K cosmic microwave background if you can look with enough resolution. Unfortunately (for observing objects, but fortunately for us) the Earth’s atmosphere is largely opaque to infrared radiation so we can’t easily spot dark objects from the ground, hence the need for solar orbiting observatories which can look in the near-infrared through low microwave spectrum, both for research astronomy and hazard detection and tracking.

Stranger

[Grey]

I think A Dodgy Dude was envisioning a simple human looking up. I haven’t worked the numbers but consider that the moon’s albedo is about 0.12 and appears very bright, both due to size and the darkness of its background. A very (very) quick look gives an asteroid albedo of 0.1 (cite: Usually given by the IRAS minor planet survey[1] or the MSX minor planet survey[2] (available at the PDS). These are geometric albedos. If there is no IRAS/MSX data a rough average of 0.1 can be used). I’d hazard a guess that by the time you could see a 10km chunk of rock coming at you, its apparent velocity might stick out… for about 10 seconds.